w00t CloudStack!<p>Some quick facts:<p>- CloudStack is the most active Apache project now by no. of commits/day and code/development activity: <a href="https://www.ohloh.net/orgs/apache" rel="nofollow">https://www.ohloh.net/orgs/apache</a><p>- Stable, mature code, used in production. Works for Xen, KVM and VMWare.<p>- Real world deployments, largest known deployment consists of some 20k hosts (source Collaboration12, I don't know exactly which talk/video, someone can comment with a link)<p>(Note, I'm a CloudStack developer and committer and I'm loving it :)